Heater doesnt change to cold

Fuses are a great place to start, if not fuses the actual cruise control switch may be to fault. Rear heater do you get heat out the front and if so is there a fuse for a rear fan maybe a blower.. Let me know

The heating coil is probably getting plugged up. You may have heat at idle or slow speeds, but once you get going, there is not enough coolant going through it to stay warm. Get the system flushed or replace the heating coil.

Need to replace the actuator these go out all the time. Bad part idea.

if you saying the fan wont blow it may need a fan motor not uncommon it might be a speed switch if it has one some time you can hook a wire on the back of the speed switch plug in to get it on high use a 14 gauge wire or bigger a small jumper bent in a loop with the rubber peeled off the ends and shove them in the switch plug find the 12 volt ht wire on the plug with light or vom then try the other wires one at a time til fan runs with ignition switch on

Either your heater control valve is not properly operating or your heater core is clogged. Locate the heater control valve under the hood, should be close to firewall on heater hose, have someone adjust temperature from hot to cold and see if you can see the heater control valve operating if so replace the heater core, if its not doing anything replace it(heater control valve).

There amy be a problem with the heater relay switch which is not allowing it to switch over to heat.

If changing the thermostat didn't work, have the heater control valve checked, it may not be opening all the way to let the coolant circulate thru the heater core fully.

air valve on heater hose missing or cracked, small 2mm vac hooks up to the control valve on bottom L shaped connector. rubber boot.

check water level in rad if ok check thermostat or couldbe a plugged heater core.also check for vacum to heater door is working